During the course of the proposed project we plan to investigate the effects of unilateral torsion of the spermatic cord on the contralateral testis in human and guinea pig. Human testicular biopsy materials, obtained at the Medical College of Ohio Hospital (during the three year period) at the time of surgery for the correction of testicular torsion, will be studied. Unilateral torsion will be induced in guinea pigs and the animals will be sacrificed at variable time intervals (l month through 24 months) to study the time-course relationship of the effect of torsion on the so-called unaffected, contralateral testis. Histological and fine structural studies on both tubular and peritubular materials will be carried out. Quantitative estimation of germ cell degeneration and Leydig cells in the contralateral testis will be carried out. At the end of this project we shall determine: i) whether the damage in one testis can affect the contralateral testis and whether this damage due to unilateral torsion is a temporary or a permanent effect; ii) whether there is a time-course relationship between the damage in the contralateral testis and retention of a badly damaged testis in the body for a variable period of time. We hope to discern the gradual function-associated structural changes in testicular tissue which may occur during progressive pathogenic alterations.